Super Cooler Code
August 13, 2014
Hi guys as some of you know I've been working on code for a project I have in mind, it not a new idea, lots of folks are doing it http://freeaire.com/ , I just want to put my take on it, and perhaps save some store owners some money and make a little myself.
I live in Maine USA, winters are pretty cold here, lots of small stores have walk in coolers for keeping beer and soda code, so why not when its suitable use that cold air to cool the walk ins, a typical 8' by 20' walking cooler costs $250 or more a month in electricity to operate.
Some design stuff
1, A typical walk in cooler for beer and soda likes to around 35F and 65-75% relative humidity, lower is ok in this application, it however would not be if we were keeping produce or flowers, those both like much higher humidity levels so lets make it totally adjustible for differant applications.
So I will use 2 cheap DHT22 sensors 1 to measure and check that the outside air is cold enough and dry enough, one to measure inside cooler temp and humidity, at certain times we may want to run existing refridgeration system to lower the coolers humidity.http://www.adafruit.com/products/385
2, We will need a fan/blower to force the cold air in, thus we need a damper or another fan to let the warm air out, we should probably prove that the damper for now is open before we start the fan. Some form of end switch should work.http://tinyurl.com/m4nuo7s I know this unit end switch could be used to start the fan and we may choose to do it that way but for now I'm going to code for the arduino to start both. A possible fan, http://tinyurl.com/o289brp. Due to the size of this fan we may wish to have more than one damper,fan setup for larger coolers. I think equipment much larger might be difficult to install, a 6" holesaw is a handful.
3, We will want a relay to put in the existing thermostat circuit to dissable the compressors while we are running our system, the relay will be normally closed and we will use arduino to pull it open, that way if there is a problem with our system the cooler defaults back to normal operation, no harm no fowl. We should also put a function or timer so that if cooler temp continues to rise we start the refridgeration system.
4, We will want a simple lcd to display data, fan on/off, temp humid in/out this is bling for the owner, when it gets serviced or adjusted, I'll hook a laptop to it. Going to use this one because I already have 2, http://tinyurl.com/kfgbkf9 , there are lots of better choices if I ever build more than 1.
5, There will be lots of other considerations as we go along, perhaps a winter/summer switch, so in the warm months we can close and insulate the penetrations we will make into the cooler. screens to keep critters like mice out, that kinda thing. So stay loose and flexible, and check building codes carefully.
6, I am going to need a test walkin cooler to play with, the owner will need to be understanding, the one I've found is in a working local gas/beer/sub/pizza joint, the cooler is approximetly 20' long, 8' wide, and 9' high, so 1440 cubic feet or so.